Pianofortes



G. HENRY HULsKAMP,

METALLIC BRIDGE PATENT OFFICE.

OF TROY, NEW' YORK.

FOR PIANOFORTES.

Specification of Letters Patent No. 17,838, dated July 2l, 1857'.

To all whom it may concern:

Be it known that l, G. HENRY Hun- KAMP, of the city of Troy, in the State of New York, havel invented some new and useful Improvements in Harmonic Metallic Bridges for Pianofortes, of which the following isla full, clear, and exact description, reference being had to the accompanying drawings, making part thereof, in which Figure l is a plan; Eig. 2 a vertical section taken atthe line A a of Fig. 1, and Figs. 3,V 4, and 5 vertical sections of portions of the improvement.

lThe same letters indicate like parts in all the figures.

To insure pure tones in pianofortes it is necessary that the strings should be held firmly in contact with the bridges at the two points which determine the vibrating length of the strings'that the points of contact should be such as to present a sufficient resistance to prevent the vibration from extending on to or beyond the bearing points and to resist the strokes of the hammer, for it is Well known that the quality of the tones is much affected by any imperfection at the bearing or supporting points. And finally it is important that the bridges or supporting surfaces should have no vibration within themselves although the sounding board bridge should communicate the vibrations of the strings to the sounding board on which it rests. In view of these results the bridges of pianofortes have been so constructed as to form bearing surfaces both above and below the strings on their passage to the pegs and pins. In this way by very slight defiections `from a straight line the strings are firmly held at the points which determine the lengths of vibration for the various tones and without reference to the position of the strings on the pegs or pins while at the same time the bearing points, where the vibrations terminate are placed above to present resistance to the upward stroke of the hammers and the strokes and vibrations are prevented from affecting either the bridge or the strings beyond the points of support.

ln the accompanying drawings ay a. represent the frame of the piano which may be of any suitable construction and b t the metal frame such as is usually employed. The bridge t' with its rest c is attached to the said iron frame in the manner hereinafter specified and between this bridge and its rest a series ofI perforations or holes d are made in the process of casting through which the strings pass from the tuning pins e to the pegs f, thus passing over and resting on the surface of the rest c and passing and bearing under the lower surface of the bridge i. ln this wvis formed a series of perforations or holes d one for the strings of each note, the bridge i being connected with the rest c by braces j, one between the strings of each note and parallel or nearly so with the strings wh en distended.

lt is manifest that when the string is drawn tightly against the lower surface of the bridge and compelled to slide along it in the process of tuning, a great degree of friction will be produced interfering with the nice adjustment of the string and often causing it to break at that point. To remedy this difficulty as far as practicable l cast the lower surface of the bridge iv with a slight cavity along its entire length in which l insert a rod or wire le made of Zinc, ivoryI wood, brass or other suitable material or composition and secure it to the bridge t' to hold it in its place. By this device the necessity oil fitting and polishing the bearing surface of the bridge i is obviatedv and while the strength of the cast iron bridge is retained the bearing is upon a material that produces less friction than would take place between steel on iron, and what is of still greater importance the bearing upon a soft material produces a soft tone without the harsh metallic sound that attends a bearing upon cast iron.

The harmonic bridge t', has heretofore been cast in one piece, solid with the frame l), l). This renders access to the lower surface diliicult either for fitting or repairs and makes it almost impossible to give to it the requisite finish and polish. l have retained the requisite soliditv and yet made it detachable by afiixing it to the lower plate O, with dove-tailed joints. For the form represented in Fig. 3, the bridge i, is cast separately in one or more pieces, the bottom face having one or more dove-tailed projections l, fitted to mortises of corresponding formin the plate C, to receive the projections Z, the said mortises being wedge formed longitudinally so that after the projections have been inserted in the widest part of the mortises by simply pushing the bridge i lengthwise it will be firmly held in place.

ln grand piano-fortes l dovetail the bridge as represented inlligh, or to projections cast upon the frame.

. -The drawing-is a cross section through the middle of the bridge i, e', when in its place.

vI cast the iangers u, u, upon the sides of the cross bars Z, Z, and the same have a length equal to the Width of the bridge i, i, and fill the corresponding mortises cast in the bridge t', t. By sliding the latter forward beyond the length of these flanges u, u, it may be taken from its place.

l have described these modifications as illustrative of the variations which may be made in the mode of applying my invention. And it may be further mentioned among its advantages that it Will enable the manufacturer who may desire to obtain the tone peculiar to any particular metal or composition tosubstitute such material for the bridge in place of cast-iron. ln this way its tone will be much improved.

/Vhen the piano is made Without an iron frame l construct the bridge as represented at Fig, 4 with two flanges lm and n, by means of which it can be secured by screws to the block o, of the wooden frame.

The sounding board bridge p, is cast in one piece of metal (or in sections if desired) and secured by screws or otherwise to the Wooden bridge. This bridge p, is also formed With a series of perforations or holes g, made in the direction of the stringsthus connecting by brace pieces 7, and making part thereof the bottom supporting surface or rest s, thence to the securing pegs f, and being slightly defiected from a straight line are sure to be kept in contact with supporting surfaces of the bridge and as there is one upper bar on each side, the tension ol' the strings will have no tendency to tilt or lift one edge of the bridge from the sounding board as would be the case if but one upper bar were employed.

What l claim as my invention and desire to secure by-Letters latent isl. The sounding board bridge cast of metal with bearings above the string one on each side of the bottom support, substantially as, and vfor the purposes specified.

2. l claim the rod or Wire lc, or its equivalent inserted in the bridge to form its bearing surface for the uses and purposes above set forth.

3. l claim the construction and arrangement of the cast metal bridge i, i, in such form that it may be detached and yet 'firmly held in its place-in the mode above set forth or other form substantially the same. i

G. HENRY HULSKAMP. Witnesses: B. Hi HALL, JOHN B. GALE. 

